1. Field of the Invention
This invention relates to ski control devices and systems and particularly to a ski control system with carve control amplification that enhances the skier's ability to control speed and maneuverability on a downhill skiing run.
2. Description of the Prior Art
This invention provides improvements on the method and structure of the Ski Control System described in U.S. Pat. Nos. 4,986,561, 4,911,461 and 5,145,200 awarded to the inventor herein. The prior art that was considered in connection with these patents and determined to be non-applicable is identified in those patents and is included herein by reference. Similarly, the method and structure of the Ski Control System on which the invention herein disclosed provides further improvements is also thoroughly described in those patents and is included herein by reference. However a brief summary is provided of the prior inventions noted as an introduction to the improvements disclosed herein.
The Ski Control System (SCS) disclosed in the patents noted above consists of control probes on a downhill ski that may be deployed into engagement with the snow. Once deployed by the skier, the SCS probes remain resiliently deployed until specifically disengaged by the skier. The probes are located near the center of pressure of the ski so that they work with the ski to provide the skier with enhanced control over both speed and maneuverability. This enhanced control over speed and maneuverability is provided using natural skiing motions without any specific skier actions or motions required just to control the probes.
A downhill ski is, in effect, a flight vehicle, as is an airplane. However, unlike an airplane, a conventional downhill ski has no control surfaces to provide enhanced speed and maneuverability control. Control of a conventional downhill ski is achieved primarily by "carving" the ski, i.e., bending the body or "fuselage" of the flight vehicle, and thereby altering the distribution of load along the longitudinal axis of the ski. This distributed load can, depending on the location of the skier's center of gravity and the angle of attack of the ski, create both turning torques as well as lift and drag loads.
Conventional skis have no control surfaces, because control surfaces on any flight vehicle inevitably add drag. Conventional skis are designed to achieve minimum drag in order to provide maximum speed for racing skiers. However for most recreational skiing situations the objective of the skier is not to go as fast as possible, but to always ski at a speed where the skis are under control. For most recreational skiers, the slopes they should ski on and the speed they should achieve are limited by their ability to control the skis rather than by the maximum speed capability of the skis. These skiers can beneficially trade a little drag for an increase in maneuverability achieved by adding control surfaces to the skis. The additional maneuverability provided by the SCS increases the skier's safe control speed defined as the highest speed at which a given skier can remain in control under a given set of skiing conditions. The increase in safe control speed both enables recreational skiers to progress more rapidly to more interesting terrain and enables cautious recreational skiers to enjoy intermediate terrain with a greater control margin between the speed at which they are skiing and their safe control speed.
An important challenge of SCS design optimization, as with all flight vehicle control systems, is to provide enhanced control forces during maneuvers while minimizing drag forces under straight skiing conditions. Maximizing this control-force to drag ratio enhances skier control on the steeper parts of a run without significantly reducing the skier's speed on the flatter parts of the run. The SCS limits control probe axial forces (drag forces imposed in the axial direction of the ski at zero ski slip angle) by using resiliently retained probes whose penetration depth automatically adjusts in response to the axial force on the probes. Since probe drag force is a strong function of the probe penetration depth into the snow, probe depth variation controls the probe axial drag forces to be no greater than the applied spring force multiplied by the mechanical advantage of the mechanism. Unfortunately since control forces are related to axial forces, limiting the axial forces to control the drag also limits the forces available to execute maneuvers.
The SCS uses several techniques to maximize the control-force to drag-force ratio. The SCS structures in this invention are designed so that the spring force that resists probe retraction increases with probe retraction angle. Under flat skiing conditions a small probe rotation under a relatively weak spring force retracts the probes from the snow to minimize flat ski drag. However when the ski is on edge during maneuvers, a much larger probe rotation is required to retract the probe from the snow. This larger rotation requires a larger spring force which ensures higher available probe loads during maneuvers. Design of the shape of the probe further improves the control to drag ratio by presenting a streamlined low control force profile for straight skiing conditions and a high control force profile during maneuvers.
The SCS enables the skier to adjust SCS forces by adjusting both the maximum probe depth and the level of probe preload. Reducing the maximum probe depth reduces flat ski drag, but requires more edging to fully engage the SCS. This enables intermediate skiers to improve the SCS control to drag force ratio on groomed snow and enables all skiers to improve the SCS control to drag force ratio on hard snow where even slight edging fully engages the SCS. Increasing probe preload above the nominal setting increases both drag and control forces. A higher preload is often useful on hard snow in conjunction with a reduced probe depth.
The primary objective of this invention is to enhance the SCS probe control to drag ratio disclosed in the above noted patents by using the carve of the ski to amplify the SCS control forces. Since the skier increases the carve of the ski whenever he puts the ski on edge to execute a maneuver, using the carve of the ski to amplify SCS control forces provides an automatic enhancement of SCS control forces during maneuvers without any additional actions by the skier. This invention achieves enhanced SCS probe control forces under carved ski conditions (which are called "Carve Control Amplification" or "CCA") by providing a mechanical feedback between the carve of the ski and the preload acting on the SCS probes. When the ski is carved, the compression of the top surface of the ski is increased and the tension of the bottom (or running) surface of the ski is increased. The Carve (SCS) Control Amplification method utilizes the increased compression (shortening) over some length of the top surface of the ski or the increased elongation over some length of the bottom surface of the ski whenever the ski is carved to increase the spring force acting on the SCS probes. The two embodiments; presented herein illustrate two ways to use either bottom ski surface tension (elongation) or top ski surface compression (shortening), respectively, to achieve SCS preload amplification as the ski is carved. However, either design could achieve ski carve amplification of SCS preload using either top surface compression or bottom surface tension or even a combination of the two.
A further objective of this invention is to develop improved SCS structures which are compatible with the use of Carve Control Amplification to achieve enhanced SCS control to drag force ratios.
The invention possesses other objects and features of advantage, some of which, with the foregoing, will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiments illustrated and described since it may be embodied in various forms within the scope of the appended claims.